The present invention relates to glycosylation variants of iduronate-2-sulfatase and to genetic sequences encoding same. The present invention also contemplates the use of these in the treatment and diagnosis of subjects suspected of, or suffering from, iduronate 2-sulfatase deficiency.
Iduronate 2-sulfatase (hereinafter abbreviated to xe2x80x9cIDSxe2x80x9d; EC 3.1.6.13) acts as an exosulfatase in lysosomes to hydrolyze the C2-sulfate ester bond from non-reducing-terminal iduronic acid residues in the glycosaminoglycans heparan sulfate and dermatan sulfate (1). IDS is one of a family of at least nine sulfatases that hydrolyze sulfate esters in human cells. They are all lysosomal enzymes that act on sulfated monosaccharide residues in a variety of complex substrates with the exception of microsomal steroid sulfatase (or arylsulfatase C), which acts on sulfated 3xcex1-hydroxysteriods (1,2). Each sulfatase displays absolute substrate specificity, making the sulfatase family an attractive model to investigate the molecular requirements for substrate binding and the catalysis of sulfate ester hydrolysis.
A deficiency in the activity of IDS in humans leads to the lysosomal accumulation of heparan sulfate and dermatan sulfate fragments and their excretion in urine (1). This storage results in the clinical disorder Hunter syndrome (mucopolysaccharidosis type II, MPS-II) in which patients may present with variable phenotypes from severe mental retardation, skeletal deformities, and stiff joints to a relatively mild course (1). It has been postulated that this clinical heterogeneity reflects different mutations at the IDS locus affecting enzyme expression, stability, or function. MPS-II is one of the most common mucopolysaccharidoses and is the only one that is X chromosome-linked (1).
In accordance with the present invention, there is provided the nucleotide sequence for a full length cDNA clone for IDS from human endothelial cells. The present invention also provides the genomic clone for IDS. More particularly, following expression of the IDS nucleotide sequence in particular cell lines, a glycosylation variant of IDS has been isolated which possesses inter alia improved half-life and/or improved uptake properties when compared to the naturally glycosylated molecule.
One aspect of the present invention provides a recombinant human iduronate 2-sulfatase (IDS) or a fragment thereof retaining enzymatic activity wherein said recombinant IDS or fragment thereof is more highly glycosylated than the naturally occurring enzyme or equivalent fragment on the naturally occurring enzyme.
Another aspect of the present invention contemplates a method for treating a patient suffering from iduronate 2-sulfatase (IDS) deficiency said method comprising administering to said patient an effective amount of a recombinant human IDS or a fragment thereof retaining enzymatic activity wherein said recombinant IDS or fragment thereof is more highly glycosylated than the naturally occuring enzyme or equivalent fragment on the naturally occurring enzyme.
Yet another aspect of the present invention is directed to a pharmaceutical composition useful in the treatment of patients suffering from iduronate 2-sulfatase (IDS) deficiency said composition comprising the more highly glycosylated IDS or enzymatically active fragment thereof referred to above and one or more pharmaceutically acceptable carriers and/or diluents.
Still yet another aspect of the present invention provides an isolated genomic DNA fragment carrying in whole or in part the IDS gene or a mutant or derivative thereof. The isolation of the genomic clone will enable gene therapy and genetic analysis of IDS deficiency diseases.